Crabs, Ammonites, Gastropods, and More! A Texas Invertebrate Sampler

[Mikrogeophagus]

Over the month of December, I've gotten the opportunity to check out several sites across the state of Texas. In my fossil interests, I have to admit that I am certainly a bit vertebrate-centric, but that does not mean I will pass up the chance to marvel at a beautiful invertebrate specimen when given the chance. For better or worse, these past four mini hunts have not really delivered on the vertebrate end, but have made up the difference in terms of inverts. I've decided to combine these smaller hunts into one report. For those with invertebrate addictions, I hope this sampler of Texas fossils will meet your medically-necessitated daily dose of invertebrate content. Enjoy!

 

Maastrichtian No Mas

Kemp Clay and Corsicana Formation

 

Leading up to my eventual move away from Austin back to DFW, I made sure to visit a nearby site that possessed some Maastrichtian exposures. Back up in Dallas, the nearest exposures of similar age are a bit of a drive, so I wanted to take the opportunity to travel to a convenient spot while I still had a chance. I had previously seen this spot mentioned in some old literature, where it was described as exposing the Kemp Clay at the top of a bluff and Corsicana below. Since I had no prior experience with these formations, I wasn't sure what to expect or what to look for in terms of identifying formations. One Saturday afternoon, I carved out a few hours to take the drive and a brief hike out to the spot. I was excited to finally hunt a stage of the Cretaceous I had never searched before. The landscape was quite dramatic and I could see out for miles. Pictures really do not do the place justice.

 

The drop from the trail to the creek bed is much higher than the picture makes it out to be.

 

After navigating my way down, I was immediately confused by the formation the creek bed was composed of. Perhaps I am just too Ozan-minded, but the shale looked almost indistinguishable from my usual Ozan hunting spots elsewhere in the area. It had that classic bluish grey color and was even filled with rather large Exogyra oysters. I began to wonder if so much time and weathering had passed that the creek had finally reached down to the Ozan far below. However, a closer inspection showed that there were some subtle key differences. The wavy shells of the oysters were not indicative of the species E. ponderosa, but instead of E. costata, which is present in the Corsicana Formation at least according to the paper I had read about the site prior. There was also a pronounced presence of tiny phosphatic bivalves that I had never seen in the Ozan. With this information, I was relieved to know that my goal of collecting in the Maastrichtian could continue without issue.

 

Some leftovers from an earlier fossil hunter. Not all of these are E. costata since they washed down from older strata upstream.

 

With little direction as to where to look first, I decided to plop down and try splitting open some chunks of mudstone that had fallen down from a grey and brown formation at the top of the cliff (Kemp Clay I'm assuming). Initially, I didn't find much, but eventually some invertebrate fossils began showing up. I was intrigued by the presence of the original shell on a few gastropods (I hadn't been to the Whiskey Bridge at this point so this was a first for me). They were ornamented, unlike the steinkerns I had been accustomed to for the entirety of my Cretaceous fossilizing career before. Unfortunately, none of them were preserved well and were more so just crushed messes too fragile to take back. In the same rocks, I came across various bivalves that were fairly nice to look at and ended up keeping an orange 2D one, though I am having a difficult time identifying it.

 

A gastropod with the original shell from the Kemp Clay(?)

 

A flattened bivalve(?) from the Kemp Clay(?). It's about 30 mm across, orange, and has thin red lines between the ribbing. At first, I wondered if it was a smushed trigonia, but I'm doubting that now.

 

Afterwards, I surface collected along the bed and climbed some of the cliff where Corsicana was exposed. There wasn't much in the way of large finds, but getting close to the ground revealed a plethora of smaller finds to be had. The first objects of interest were highly detailed button corals. The closest thing I could find online as an ID was the genus Micrabacia which is known from the Peedee formation (also Maastrichtian). I came across a couple bits of crab claws as well. My vertebrate hopes for ginglymostoma were never fulfilled, sadly. Instead, I found only three sharks teeth that were all missing roots . I don't think they can be identified, but I welcome you all to toss out ideas if you have any.

 

An in situ of what could be a Micrabacia button coral.

 

As I walked along the cliffs, I couldn't help but think about the time period I was traversing through. In the formations beneath me were the Cretaceous layers I had grown so used to. In those days, mosasaurs and dinosaurs dominated the world. It's mind boggling to realize that the strata just above the Kemp Clay was the geological blink of an eye that saw an end to all of it. All those billions of ammonites and not a single one made it through such a barrier. Even something so simple yet prolific like exogyra was put to a complete stop. The Maastrichtian was not a final stand by any means either. That day 66 million years ago may have started just like any other, but ended with the world being permanently changed in a way that is almost unimaginable. Speaking of days ending, the time was 30 minutes till sunset. 

 

With the day winding down, I decided to circle back and try splitting some more mudstones from the Kemp Clay in hopes of finding a shark tooth before calling it quits. Rock after rock, I couldn't seem to find anything other than the usual tiny clams and crushed snails. As the light started to dim, I was finally greeted by the sheen of shiny black enamel.

 

 

It had a strange shape to it, but this being a new place for me, it could have just been a weird shark for all I knew. As I chipped away at the rock, more and more of the specimens figure was revealed. 

 

 

Finally, I realized that all of my labor had been put into exposing a simple enchodus fang, no different from the hundreds I had seen before! And yet, I was still happy with it. After the disappointment of the broken shark teeth from before, it was nice to at last have a complete tooth from the Maastrichtian, no matter how common the animal may be. With that, another stage of the Cretaceous was crossed off the list.

 

 

Some pics of all of the finds:

 

Strange bivalve, a gastropod, Micrabacia(?) corals, and perhaps a scaphopod?

 

Top row L to R: Crustacean claw bits, and the enchodus (petrosus?) fang.

Bottom L to R: Worm tube, and three rootless shark teeth

 

 

 

Eocene Escargot

Stone City Formation

 

Fast forward about a week, and the time had come for me to pack my things and leave my dorm once and for all. I usually drive straight to Dallas from Austin, but this year things were different. My carless brother started his first semester at A&M, so I volunteered to pick him up on the way home for the break. Being the person that I am, I simply cannot drive all the way out there and NOT visit the world-class site known as the Whiskey Bridge. I made sure to turn in my dorm key early in the morning and head on out for a quick hunt in the Stone City Formation along the Brazos. I was hoping @Jared C could join in the fun, but he unfortunately had a final that same morning . I'm pretty sure passing the class wasn't that important, but I won't hold it against ya . Before making the drive, I had also done a bit of research into which layers yielded the most vertebrate material. Even with the information, however, I still had measured expectations as the Stone City Formation is of course much more famous for its rich invertebrate fauna. The goal for the day was to find some vertebrate material and perhaps a complete cone snail.

 

When I arrived, the place was still covered in mud from the storm a couple days before. With hopes that the popular site had been replenished, I carefully made my way down to the water, passing by a couple of hunters just finishing up their session. The plan was originally to head straight for a productive spot a ways from the bridge, but of course the newness of the place and its fauna had me stopping in my tracks every few steps to pick up a gastropod. When I finally got to the spot, I slowly climbed up the slope to meet the fine hash layers atop the ledge. There is never a dull moment at this locality. Every square inch of surface is covered with bits of white shell. The first oddball that caught my eye was a strange looking piece of coral.

 

Madracis johnsoni

 

Side stepping to the right while hugging the wall of soil led me to my next noteworthy find and the first of the vertebrates! The skinny crown and wrinkling of the enamel was a familiar sight for someone who has collected so many scapanorhynchus teeth in the past. However, it would seem that, for this formation, a sand tiger shark was the more likely ID. I'm guessing this is from Striatolamia macrota. The weathering on it is likely due to prehistoric reworking I would assume. 

 

Striatolamia macrota?

 

Not so long after, I sidestepped my way into finding my first ray plate! Unfortunately this one was also in not-so-perfect condition.

 

Myliobatis sp. fragment

 

I couldn't stick around for too long since my brother was waiting for his pickup. I rounded off the trip by filling up a couple bags with fine shell hash matrix for future screening for microfossils. I didn't take too much though, as I have a secret side project involving many bags of micromatrix that is currently occupying most of my micro attention. If I find anything special from the hash, I will be sure to add an update to this topic.

 

Overall, it was a solid first visit to a famous site. I managed to find some vertebrate bits and bobs that I'm happy with. I am a little bummed I never got a complete cone snail, but I guess that will just have to wait for a future outing.

 

Overview of the finds:

 

Top: Dentalium scaphopods

Bottom L to R: Striatolamia macrota tooth, Myliobatis ray tooth fragment, reworked Carcharhinus mancinae? tooth, and Conus sauridens fragments

 

Top L to R: Lunulites bouei and Schizorthosecos sp. bryozoans, and Turbinolia pharetra coral.

Bottom L to R: Fish otoliths (not sure how/don't want to ID), Balanophyllia desmophyllum, and Madracis johnsoni

 

Top L to R: Weathered Architectonica elaborata?, and probably Venericardia densata that looks strange since it doesn't seem to curve like others.

Mid L to R: Anomia ephippioides, Vokesula smithvillensis, Notocorbula texana, and perhaps a worm tube?

Bottom L to R: Large Anomia ephippiodes, and a trio of Venericardia densata

 

Top L to R: Athleta petrosus, Ancilla staminea, and Pseudoliva vestusa

Bottom L to R: Athleta lisbonensis, Architectonica scrobiculata, and Sinum arctatum

 

Top: Michela trabeatoides

Bottom L to R: Protosurcula gabbii, Hesperiturris nodocarinatus, Cochlespira engonata, and Protosurcula gabii though they look different from the one on the left of the row.

 

Top L to R: Distorsio septemdentata, and Latirus moorei

Bottom L to R: Mesalia clairbornensis, Turritella nasuta, and Gegania anitquata

 

Phew that was a lot to identify. I'm sure I got plenty wrong, so feel free to correct me on any of these. I will probably find a ton of new species in the micro matrix that I can add in a later update!

Edited December 30, 2022 by EPIKLULSXDDDDD
Formatting; Seems I hit the photo limit :P

[Mikrogeophagus]

Badlands of North Texas

Grayson Marl

 

Pretty quickly after getting settled back in DFW, my mind was already set on planning the next trip. Austin and DFW share a lot of formations, but there are many that can only be found up North. It had been a while since I had hunted these unique formations, so I was itching to get back in business and check them out. I played it risky going to a Woodbine site first and was thoroughly skunked. I decided to play it safe with the next hunt and check out a very promising-looking site in the Grayson Marl, likely just under its contact with the Woodbine. I must admit that I've been recently inspired to check out this formation because of the fantastic posts made by @Aidan Campos as well as posts on facebook by various local hunters. There seems to be a wonderfully diverse fauna that I had previously not realized existed. Sorry to all the Grayson fans, but I used to write it off as boring grey limestone. Well, now I know better! Anyways, I waited for a day when the weather was a bit nicer and headed out for a short drive to the place.

 

As I stepped out of my car and took in the view, I immediately recognized the locality as being what I had seen on multiple sites, including fb and north texas fossils. If the familiar view wasn't proof enough, the countless scattered boot prints from the previous rain was enough to tell me this was a local hotspot of sorts. Though there would be some heightened hunting pressure, this was certainly a place that could produce some fantastic specimens as I had already seen online. My mind became filled with images of Goniophorus scotti and cidarids. A rare ptychodus or any shark tooth for that matter would also be quite nice.

 

As I traversed the fields to the exposure, the place began to more and more resemble a miniature badlands. The lack of vegetation meant that rain and wind had free range to carve out many plateaus of muddy shale. Each grey mound was topped with a red cap of what I presume to be the base of the Dexter Sands. Dotted all around each plateau were numerous pyritic fossils, along with shell bits and iron rich nodules. Everything here was miniaturized. Some things were in decent condition, but most had blown up from exposure to the elements. It was clear from the start that this would be a day of crawling.

 

After about an hour of gathering small gastropods and a couple of devils toenails, I at last came upon a more notable find. Resting upon a pedestal of hardened matrix was a perfectly prepped little Goniophorus scotti - just what I had been hoping for! I made sure to stash it in my rare/fragile bag, away from the more common finds before moving along.

 

A tiny Goniophorus scotti. Apologies for the blurry in situ.

 

I quickly came to learn that this site was extremely diverse. Every 10 minutes or so, I came across a new variety of bivalve, echinoid, etc. The preservation of each specimen was also generally very good. I was hoping for the shark teeth to start rolling in at some point, but I assumed they had already been picked over awhile ago since they are easier to spot. At my final section of unexplored badlands, I knelt down one last time to finally meet the shine of enamel I had been searching for. It wasn't the most remarkable tooth, but I was excited nonetheless to come out with something in the vertebrate department. I'm not totally sure on the differences between Cretalamna catoxodon vs C. appendiculata, but I will defer to Aidan's wonderful identifications for Grayson micromorphs as he seems to have a much better grasp on this stuff than do I .

 

Cretalamna catoxodon

 

And so, another successful hunt at a productive site was in the books. I didn't quite find as much as I had hoped, but I think after a little bit of rain, I may try to head back and beat the crowd to find some of the real goodies.

 

An overview of the finds:

 

Cretalamna catoxodon

 

Goniophorus scotti

 

L to R: Texigryphaea roemeri, Neithea texana, and Plicatula incongrua

 

Top L to R: Stereocidaris hemigranosus, and Coenholectypus castilloi?

Bottom: Goniophorus scotti

L to R: Mess of worm tubes, Cretalamna catoxodon, and Parasmilia graysonensis

 

Top L to R: Praescabrotrigonia emoryi fragment, and Mariella bosquensis

Bottom L to R: Perhaps a trigonia fragment, a couple bivalves, and an assortment of gastropods

 

 

 

Some Sites Age Like Wine

Pawpaw Formation

 

Following the success of my brief trip into the Grayson, I soon decided to take on another short excursion. The cold of winter convinced me to not have a gander at one of the many potential Eagle Ford creek sites I had circled, and instead stick to places a bit drier. The locality at the top of my list for exploration was none other than the place in which I had found the Engonoceras serpintinum shown in my profile pic. It's a construction site I visited on an impromptu adventure this most recent summer. Back then, I found a decent variety of Mainstreet and Pawpaw fauna. I was mostly just crossing my fingers that development hadn't moved so fast as to cover up the exposures I had scoured before. The plan was to take only a quick hour long perusal of the area to assess whether it was still productive. I had no idea what I was getting into!

 

As I pulled into the site, I was relieved to see the old exposure still mostly free of construction (though some houses were getting dangerously close). At the top were chunks of Mainstreet Limestone, followed by an underlying red sandstone layer, and lastly an underlying grey shale layer. From my previous experience, the most interesting things to find were the cephalopods that eroded out of the red layer, so I headed for that first. After navigating over some slippery mud to the ambience of distant Mexican music, I made it to the base of the hillside. Already I could see tons of little pyritic microfossils littering the ground. I immediately knew something was up when I found a perfect Engonoceras serpintinum within 15 minutes. For reference, it took me about 3 hours straight of hunting last summer to find one of these... and that was the best thing I had found that day.

 

Engonoceras serpintinum

 

Of course this got me excited. I got real close to the ground and began carefully examining every pebble. Not so soon after, I spotted a fragment of crustacean claw. This wasn't a new kind of fossil to me, but it was new for the site. Three more crustacean bits popped up in quick succession. With a frequency of claw chunks as high as this, I could almost taste my first carapace. The crustacean fossils seemed to be concentrated around the grey shale, so I began honing in on that layer instead of the others. It didn't take long before I came across a piece of carapace. It looked strange, but examining it afterwards showed that is was mostly the abdomen of a crab.

 

Crab abdomen

 

From there, the frenzy was on to find all I could with the last hour of daylight. Ammonites of many varieties were absolutely everywhere. I had several decent engonoceras as well as heteromorphs and the first baculites I've found in the Pawpaw. There were so many crustacean claw bits, I had to stop picking them up - something I had not expected to ever happen. More complete carapaces rolled in at a steady rate from a variety of crab species. It's hard to believe this was the same site as before. It feels like fossil spots tend to go down hill after their initial exposure, but this place seemed to do the exact opposite.

 

Steorrosia aspera with a nicely preserved underside

 

The time flew by and it was already dark. Even with my quick pace, I had only managed to pick through half of the site. My rare/delicate ziploc was just as heavy as my common ziploc which is a difficult feat! Content with the day, I packed my things and headed home, saving the rest of the exposure for a future hunt. Funnily enough, I had actually picked up fresh blue crab from the market only a handful of hours earlier. Perhaps that gave me the good luck I needed to cross this Pawpaw milestone.

 

 

An overview:

 

Engonoceras serpintinum

 

 

Top L to R: Mariella worthensis, Stoliczkaia worthense, and unknown ammonite

Bottom: Baculites comanchenis?

 

L to R: Various claw fragments, fish vertebrae, lobster fragment

 

Top L to R: Steorrosia reidi carapce fragments, Texicancer renfroae, and piece of maybe Steorrosia pawpawensis

Bottom L to R: Steorrosia aspera, and Feldmannia wintoni

 

Feldmannia wintoni close ups

 

That about rounds up the past month. There wasn't much in the way of vertebrates, but with how things went, I couldn't be more satisfied. I also mentioned that I only hunted half of the Pawpaw exposure. Well, I just finished the other half a day ago and it got even better, but I won't spoil what I found. I'll be writing a new, much shorter post for that trip on its own so stay tuned!

 

 

Thanks for reading!

[Jared C]

1 hour ago, EPIKLULSXDDDDD said:

Maastrichtian No Mas

Kemp Clay and Corsicana Formation

 

I know this site! I had no idea it was in literature, I assumed it was a secret between one other hunter and I . Those vistas are certainly breathtaking, and I found the elm/oak savannah on the other side of the creek so attractive that I've considered quietly pitching a tent there one day. You made good finds for that area - I've only hit it really hard once, and came away skunked, though I've seen your elusive Ginglymostoma (or perhaps some other nurse shark - not my strong suit) found there before. 

 

1 hour ago, EPIKLULSXDDDDD said:

I was hoping @Jared C could join in the fun, but he unfortunately had a final that same morning . I'm pretty sure passing the class wasn't that important, but I won't hold it against ya .

the little devil on my shoulder was telling me to skip class for it, believe me 

 

56 minutes ago, EPIKLULSXDDDDD said:

I'm not totally sure on the differences between Cretalamna catoxodon vs C. appendiculata

Siversson et al. suggested that C. appendiculata is restricted to the Turonian of Europe. This opened a can of worms, since C. appendiculata is historically a waste bucket taxon, so it was split into several new species, while still leaving many Cretolamna morphologies in various geographical and temporal ranges abandoned into a sort of nomenclature limbo. We dug into a good discussion about it in this thread:

 

Edited December 30, 2022 by Jared C

[historianmichael]

It looks like you have a few different Maastrichtian corals. A couple could be Micrabacia, but I would have to see the top to the ones that are upside down in the photo. The other others are trochiform, kinda like Trochocyathus, but I am not sure that fits.

Edited December 30, 2022 by historianmichael

[Mikrogeophagus]

9 hours ago, Jared C said:

I know this site! I had no idea it was in literature, I assumed it was a secret between one other hunter and I 

This place was mentioned to me by another hunter, but it was already on my radar by that point. I've sent you the source for the paper that mentions it. You may have seen it before, but it's filled with so much info, I couldn't imagine retaining everything it says after just one read through. Have you posted your hunt there? I wonder if you found similar things or if it turned out different!

 

9 hours ago, Jared C said:

Siversson et al. suggested that C. appendiculata is restricted to the Turonian of Europe. This opened a can of worms, since C. appendiculata is historically a waste bucket taxon, so it was split into several new species, while still leaving many Cretolamna morphologies in various geographical and temporal ranges abandoned into a sort of nomenclature limbo

Hm I should have expected as much. Looks pretty messy . Hopefully it'll be cleared in the next decade so I'll have some peace of mind.

 

3 hours ago, historianmichael said:

It looks like you have a few different Maastrichtian corals. A couple could be Micrabacia, but I would have to see the top to the ones that are upside down in the photo. The other others are trochiform, kinda like Trochocyathus, but I am not sure that fits.

I had assumed they were the same species, just at different sizes/ages. Looking at them again, I see they are different like you mentioned. The ones on the left are horn shaped whereas the right are more disc-like:

 

 

Now that I'm looking again on Google, I've found this image which clearly differentiates two corals similar to mine. This pic is in reference to the Mount Laurel Fm which is in the northeastern US late Campanian to early Maastrichtian according to wikipedia.

 

Good catch!

[historianmichael]

1 hour ago, EPIKLULSXDDDDD said:

I had assumed they were the same species, just at different sizes/ages. Looking at them again, I see they are different like you mentioned. The ones on the left are horn shaped whereas the right are more disc-like:

 

 

Now that I'm looking again on Google, I've found this image which clearly differentiates two corals similar to mine. This pic is in reference to the Mount Laurel Fm which is in the northeastern US late Campanian to early Maastrichtian according to wikipedia.

 

Good catch!

 

I think you can safely say that the ones on the left are in the family Caryophyllidae.

 

The ones on the right are still a little fuzzy. Micrabacia is probably a good guess.

 

I have found both in the Late Maastrichtian Prairie Bluff Chalk, so they fit time-wise with your Maastrichtian-aged exposure.

 

 

 

Edited December 30, 2022 by historianmichael

[PaleoPastels]

I always love how you write your trip reports, always full of details like we were there too! 
 

Amazing finds as always! You always have a great eye for the smaller stuff- I know I already freaked out over your pawpaw crab find but seeing it with all the other crabs is so fun! So happy for you!  Gonioporus s. and all the Engonoceras are also my favorites! 
 

Welcome back to DFW! 

[PFOOLEY]

I've come back to this post a few times now...pretty darn good trips report. I will definitely be watching for your future posts.

 

Love some good Cretaceous reporting.

 

[Wrangellian]

Just found this thread, probably due to PFOOLEY refreshing it....

Lots of goodies! How can you not collect inverts when there are such spoils to be had in your area?

I like the corals in particular, probably because I find a similar one up here (not the same genus, Santonian age). Mine are somewhat variable but I think they're all from one species.

Edited January 7, 2023 by Wrangellian

[GPayton]

I don't think I've ever been as jealous of a fossil the size of a fingernail as I am right now - that Feldmannia is incredible! 

I've hunted the Grayson Marl many times myself (mostly the Waco Pit before it closed down) and I was lucky to come away with just two minuscule claw fragments from over 20 different trips. I'd probably pass out on the spot if I ever saw anything close to as breathtaking as that crab carapace.